JP6497001B2 - Thermosetting resin composition and solar cell back surface protective sheet - Google Patents

Description

  The present invention relates to a thermosetting resin composition containing an emulsion of an acrylic polymer, and a solar cell back surface protection sheet using the thermosetting resin composition.

Conventionally, an acrylic polymer is a resin having excellent properties such as weather resistance, flexibility, adhesion, and chemical resistance, and has been used in various applications.
For example, acrylic polymers can be used for various coating agents (for cans, building materials, construction, automobiles, home appliances, solar cell back surface protection sheets, etc.) and various adhesives (for building materials, construction, optical parts, Widely used in applications such as automotive parts, solar cell back surface protection sheet, solar cell module, etc.

  Acrylic polymers include water-based (water-soluble, water-dispersed) and organic solvent-soluble types, and water-based acrylic polymers include water-soluble and water-dispersed. References 1 to 4 disclose various water-dispersed acrylic polymers.

JP 2003-165803 A JP 2003-176411 A Japanese Patent Laid-Open No. 11-1597 JP-A-8-3409 Japanese Patent Laid-Open No. 11-80485

The coating film obtained from the water-dispersed acrylic polymer is generally superior to the coating film obtained from the water-soluble acrylic polymer in terms of water resistance and solvent resistance. However, the required performance is becoming strict and further improvements are required.
An object of the present invention is to use a thermosetting resin composition containing an emulsion of an acrylic polymer capable of forming a cured coating film having excellent water resistance and solvent resistance, and the thermosetting resin composition. It is providing the solar cell back surface protection sheet which consists. Furthermore, it is providing the solar cell module which uses the said solar cell back surface protection sheet.

The inventors of the present invention use an acrylic polymer emulsion (A) containing a water-insoluble component having a small hydroxyl group content and a water-insoluble component by using a monomer having a hydroxyl group and rich in hydrophobicity. By this, it discovered that the cured coating film excellent in water resistance and solvent resistance could be provided.
That is, the present invention is a glass obtained by polymerizing an acrylic monomer (a) having an hydroxyl group and having an acrylic monomer (a1) having an aqueous solubility at 25 ° C. of 75 μg / mL or less as an essential component in an aqueous medium. The present invention relates to a thermosetting resin composition containing an acrylic polymer emulsion (A) having a transition temperature of −40 ° C. to 100 ° C. and a blocked polyisocyanate compound (B1).

The acrylic polymer emulsion (A) has a hydroxyl value of 1 to 200 mgKOH / g in the solid content of the acrylic polymer emulsion (A), and the hydroxyl value of the water-insoluble component contained in the acrylic polymer emulsion (A). Is preferably 1 to 150 mgKOH / g.
The acrylic monomer (a1) having a hydroxyl group and having a solubility in water at 25 ° C. of 75 μg / mL or less is polypropylene glycol monoacrylate, polypropylene glycol monomethacrylate, 4-hydroxybutyl methacrylate, 1,4-cyclohexane. Dimethanol monoacrylate, 1,4-cyclohexanedimethanol monomethacrylate, 2-hydroxybutyl acrylate, 2-hydroxybutyl methacrylate, polypropylene glycol monomethacrylate, 5-hydroxypentyl methacrylate, and unsaturated fatty acid hydroxyalkyl ester modified ε-caprolactone It is preferable that it is at least one selected from the group consisting of
The molar ratio of the hydroxyl group in the acrylic polymer to the isocyanate group in the blocked polyisocyanate compound (B1) is preferably NCO / OH = 0.1-15.

Moreover, this invention is a solar cell back surface protection sheet which has a thermosetting adhesive resin layer (4 ') as an outermost surface layer on one side of the plastic film (2),
The thermosetting adhesive resin layer (4 ′) is formed from the thermosetting resin composition, and the thermosetting adhesive resin layer (4 ′) has 0 insoluble matter with respect to methyl ethyl ketone. It is related with the solar cell back surface protection sheet which is -50weight%.

Furthermore, the present invention provides a solar cell surface protection member (I) positioned on the light receiving surface side of the solar cell, a sealant layer (II) positioned on the light receiving surface side of the solar cell, a solar cell (III), and a solar cell A solar cell module comprising the sealing agent layer (IV) positioned on the non-light-receiving surface side and the solar cell back surface protective sheet, which is in contact with the non-light-receiving surface side sealing agent layer (IV). And
The present invention relates to a solar cell module, wherein a cured adhesive layer (4) formed from the curable adhesive resin layer (4 ′) is in contact with the non-light-receiving surface side sealing agent layer (IV).

  According to the present invention, it is possible to provide a thermosetting resin composition containing an emulsion of an acrylic polymer that can form a cured coating film that is excellent in water resistance and solvent resistance, and is excellent in adhesion, adhesion, and durability. did it.

The typical sectional drawing of the conventional or solar cell module of this invention is represented. The typical sectional view of an example of the solar cell back surface protection sheet of the present invention is expressed. The schematic sectional drawing of the other aspect of the solar cell back surface protection sheet of this invention is represented.

  Hereinafter, the present invention will be described in detail. Needless to say, other embodiments are also included in the scope of the present invention as long as they meet the spirit of the present invention. In addition, the numerical value range specified by using “to” in this specification includes numerical values described before and after “to” as ranges of the lower limit value and the upper limit value. In this specification, “film” and “sheet” are not distinguished by thickness. In other words, the “sheet” in this specification includes a thin film-like material, and the “film” in this specification includes a thick sheet-like material.

The acrylic polymer emulsion (A) of the present invention will be described.
As compared with the case where only a hydrophilic monomer is used as an acrylic monomer having a hydroxyl group, the present inventors use a monomer having a hydroxyl group and a hydrophobic property, which is contained in the emulsion (A). It has been found that the content of water-soluble components can be reduced and hydroxyl groups can be actively introduced into the water-insoluble components contained in the emulsion (A).
The acrylic polymer emulsion (A) is a polymer of an acrylic monomer (a) having an hydroxyl group and having an acrylic monomer (a1) having a water solubility at 25 ° C. of 75 μg / mL or less as an essential component in an aqueous medium. An acrylic polymer emulsion having a glass transition temperature of -40 ° C to 100 ° C. The solubility of the hydroxyl group-containing hydrophobic acrylic monomer (a1) in water at 25 ° C. is more preferably 25 μg / mL or less. The acrylic monomer (a1) is also referred to as a hydroxyl group-containing hydrophobic acrylic monomer (a1) and a hydroxyl group-containing hydrophobic acrylic monomer (a1).

When the acrylic monomer having a hydroxyl group used in the acrylic polymer emulsion (A) has a solubility in water at 25 ° C. of more than 75 μg / mL, the crosslinking between the adhesive and the plastic film becomes sparse, and the moisture resistance of the coating film The heat property is lowered, and the adhesive force to the sealant is lowered after the wet heat test.

When an acrylic monomer having a hydroxyl group is copolymerized with another acrylic monomer to produce an acrylic polymer emulsion, the hydroxyl group-containing acrylic monomer is sufficiently copolymerized with the other acrylic monomer to have an almost constant composition. In the past, it was thought to produce an emulsion of an acrylic polymer.
However, when only an acrylic monomer having a hydroxyl group rich in hydrophilicity is used, a part of the hydroxyl group-containing hydrophilic acrylic monomer is copolymerized with another acrylic monomer to form a copolymer. Some are presumed to form water-soluble homopolymers. That is, it is considered that hydroxyl groups are localized in the water-soluble homopolymer, and that there are fewer hydroxyl groups in the hydrophobic copolymer that is the main component for forming a cured coating film.
On the other hand, when an acrylic monomer having a hydroxyl group is used not only having a hydrophilic property but also having a hydrophobic property, the formation of a water-soluble homopolymer can be suppressed, and the polyisocyanate compound (B) described later It is possible to positively introduce a hydroxyl group as a reaction site with the hydrophobic copolymer. As a result, since a dense cross-linked structure can be formed by reaction with the polyisocyanate compound (B), it is considered that a cured coating film having excellent water resistance and solvent resistance could be formed.
These estimations and considerations are supported by the hydroxyl value of the solid content of the acrylic polymer emulsion (A) described later and the hydroxyl value of the water-insoluble component contained in the acrylic polymer emulsion (A).
The “water-soluble homopolymer” means a water-soluble polymer formed mainly from a water-soluble acrylic monomer rich in hydrophilicity, and completely denies the copolymerization of other monomers. It is not a thing.

  The solubility in water at 25 ° C. means the weight of monomer (G) dissolved in 1 mL of water at 25 ° C. A measurement method will be described. After adding 20 g of monomer to 100 mL of water and stirring, 1 mL of the aqueous phase was taken and analyzed by high performance liquid chromatography (HPLC), and the amount of monomer detected was converted to weight to determine solubility. Even when the monomer is highly hydrophobic and the amount of monomer dissolved in 100 mL of water is 0.1 g or less, it is expressed as 1 μg / mL. Similarly, the monomer is highly hydrophilic and the amount of monomer dissolved in 100 mL of water is 20 g or more. Even in this case, the concentration is 200 μg / mL.

Examples of the hydroxyl group-containing hydrophobic acrylic monomer (a1) include 1,4-cyclohexanedimethanol monoacrylate, 1,4-cyclohexanedimethanol monomethacrylate, 4-hydroxybutyl methacrylate, 2-hydroxybutyl acrylate, and 2-hydroxybutyl. Examples include methacrylate, polypropylene glycol monomethacrylate, 5-hydroxypentyl methacrylate, and unsaturated fatty acid hydroxyalkyl ester modified ε-caprolactone.
Examples of the hydroxyl group-containing hydrophilic acrylic monomer include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, and the like.
The solubility of these hydroxyl group-containing acrylic monomers in water at 25 ° C. is given below.

The acrylic polymer emulsion (A) of the present invention essentially comprises the hydroxyl group-containing hydrophobic acrylic monomer (a1), and the hydroxyl group-containing hydrophilic acrylic monomer and other various acrylic monomers in an aqueous medium. It can be obtained by polymerization.
Examples of the copolymerizable monomer include an acrylic monomer having an alkyl group (the hydroxyl group-containing hydrophobic acrylic monomer (a1), the hydroxyl group-containing hydrophilic acrylic monomer, a monomer having a carboxyl group, a monomer having a glycidyl group. In addition to acrylic monomers having a carboxyl group, acrylic monomers having a glycidyl group, and the like, vinyl acetate, maleic anhydride, vinyl ether, vinyl propionate, styrene, and the like can be mentioned. It preferably has a carboxyl group.

Examples of acrylic monomers having an alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, normal butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, cyclohexyl (meth) acrylate, and the like. Can be mentioned.
In addition, methyl (meth) acrylate means at least one of methyl acrylate or methyl methacrylate, and the same shall apply hereinafter.

  Examples of the (meth) acrylic monomer having a carboxyl group include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, and citraconic acid.

  Examples of the (meth) acrylic monomer having a glycidyl group include glycidyl acrylate, glycidyl methacrylate, and 4-hydroxybutyl acrylate glycidyl ether.

  The acrylic polymer emulsion (A) of the present invention is a polymer (emulsion polymerization, suspension polymerization, etc.) of the above acrylic monomer group in an aqueous medium using a water-soluble or oil-soluble radical polymerization initiator. Can be obtained. In the polymerization, an emulsifier (surfactant) can be used.

  Examples of radical polymerization initiators include sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide, t-butyl peroxybenzoate, t-butyl hydroperoxide, 2,2-azobisisobutyronitrile, 2 , 2-azobis (2,4-dimethylvaleronitrile), 2,2-azobis (2-diaminopropane) hydrochloride, etc., but potassium persulfate, sodium persulfate, and ammonium persulfate are preferably used. .

As the emulsifier, anionic, cationic, nonionic or amphoteric ones can be used alone or in combination. Moreover, you may use the reactive thing which has a radical double bond.
Examples of anionic emulsifiers include alkylbenzene sulfonic acid (product name: Rypon LS-250 [manufactured by Lion Corporation]), polyoxyalkylene alkyl ether sulfate ammonium (product name: Eleminol CLS-20 [manufactured by Sanyo Chemical Industries]), and the like. Is mentioned.
Examples of cationic emulsifiers include lauryltrimethylammonium chloride (product name: Kathiogen TML [Daiichi Kogyo Seiyaku Co., Ltd.]), octyldimethylethylammonium ethyl sulfate (product name: Catiogen ES-L [Daiichi Kogyo Seiyaku Co., Ltd.]). ) And the like.
Examples of nonionic emulsifiers include polyoxyethylene alkyl ether (product name: Emulgen E1118S-70 [manufactured by Kao Corporation]), polyoxyethylene distyrenated phenyl ether (product name: Emulgen A-60 [manufactured by Kao Corporation]) Etc.
Examples of amphoteric emulsifiers include lauryldimethylaminoacetic acid betaine (product name: Amogen S [Daiichi Kogyo Seiyaku Co., Ltd.]), aminopropionic acid (Enagicol DP-30 [manufactured by Lion Corporation]), and the like. Examples of reactive emulsifiers include ether sulfate-type ammonium salts (product name: Adecalia Soap SR-10 [manufactured by ADEKA)], polyoxyethylene nonylpropenyl phenyl ether (product name: Aqualon RN-20 [Daiichi Kogyo Seiyaku Co., Ltd.] Etc.]).

The hydroxyl value of the solid content of the acrylic polymer emulsion (A) is preferably 1 to 200 mgKOH / g, more preferably 1 to 130 mgKOH / g, and still more preferably 1 to 110 mgKOH / g. The hydroxyl value of the water-insoluble component contained in the acrylic polymer emulsion (A) is preferably 1 to 150 mgKOH / g, more preferably 1 to 120 mgKOH / g, and 1 to 100 mgKOH / g. More preferably it is.
The solid content is obtained by removing moisture from the acrylic polymer emulsion (A) by drying, and the water-insoluble component is separated from the aqueous phase by centrifugation of the acrylic polymer emulsion (A). It is a component.

If only an acrylic monomer rich in hydrophilicity is used as the acrylic monomer having a hydroxyl group, the water-soluble component increases. Then, the hydroxyl value of the water-insoluble component contained in the acrylic polymer emulsion (A) is smaller than the hydroxyl value of the acrylic polymer emulsion (A) simply dried. On the other hand, when a hydrophobic acrylic monomer is used as the acrylic monomer having a hydroxyl group, the water-soluble component decreases and the water-insoluble component increases. The difference between the hydroxyl value of the solid content obtained by simply drying the acrylic polymer emulsion (A) and the hydroxyl value of the water-insoluble component contained in the acrylic polymer emulsion (A) is reduced.
From this, as described above, when only an acrylic monomer having a hydroxyl group having a high hydrophilicity is used, the acrylic monomer having a hydroxyl group mainly forms a water-soluble homopolymer, and a water-insoluble component. It is thought that the hydroxyl groups contained therein are reduced. As a result, the number of reaction points between the water-insoluble component and the polyisocyanate compound (B) is reduced, and a dense cross-linked structure cannot be formed. Therefore, it is considered that a cured coating film excellent in water resistance and solvent resistance cannot be formed. .
From the viewpoint of further suppressing the production of water-soluble components, it is preferable to use only a hydrophobic acrylic monomer as the acrylic monomer having a hydroxyl group.

  When the hydroxyl value of the water-insoluble component of the acrylic polymer emulsion (A) exceeds 150 mgKOH / g, the cured coating formed by the reaction with the polyisocyanate compound (B) becomes densely crosslinked, resulting in a plastic film. There is a risk that the adhesive strength of the material will be reduced. Moreover, even if it is initially bonded, the crosslinking reaction proceeds during the moist heat test, and the adhesive force may decrease after the moist heat test. On the other hand, when the hydroxyl value of the water-insoluble component of the acrylic polymer emulsion (A) is less than 1 mgKOH / g, the cured coating film is poorly crosslinked, and the cured coating film is deteriorated in moisture and heat resistance. Adhesive strength to the agent is reduced.

The measurement of the hydroxyl value of the water-insoluble component will be described.
Centrifuge the acrylic polymer emulsion (A) with a centrifuge (30000 rpm, 1 hour), remove the supernatant, add the same amount of water as the removed supernatant, and centrifuge again (30000 rpm, 1 hour). And removing the supernatant solution and drying the precipitated components to obtain a water insoluble component. About 1 g of a sample obtained by drying the obtained water-insoluble component to give a solid content of 100% is accurately weighed into a stoppered Erlenmeyer flask, and 100 ml of pyridine is added and dissolved at 100 ° C. Further, exactly 5 ml of an acetylating agent (a solution in which 25 g of acetic anhydride was dissolved in pyridine to make a volume of 100 ml) was added and stirred at 100 ° C. for about 1 hour. To this, phenolphthalein reagent is added as an indicator and lasts for 30 seconds. Thereafter, the solution is titrated with a 0.5N alcoholic potassium hydroxide solution until the solution becomes light red.
The hydroxyl value was determined by the following formula. The hydroxyl value was a numerical value in the dry state of the resin (unit: mgKOH / g).
Hydroxyl value (mgKOH / g) = [{(ba) × F × 28.05} / S] / (Nonvolatile content concentration / 100) + D
Where S: Sample collection amount (G)
a: Consumption of 0.5N alcoholic potassium hydroxide solution (ml)
b: Consumption of the 0.5N alcoholic potassium hydroxide solution in the blank experiment (ml)
F: Potency of 0.5N alcoholic potassium hydroxide solution D: Acid value (mgKOH / g)

It is important that the glass transition temperature (Tg) of the acrylic polymer emulsion (A) is −40 to 100 ° C., preferably −30 to 90 ° C., more preferably −20 to 70 ° C. When Tg exceeds 100 ° C., the cured coating film becomes hard and the adhesive force to the sealant is reduced. Moreover, when it is less than -40 degreeC, a cured coating film becomes soft and the adhesive force after a moist heat resistance test falls. Moreover, since tack occurs on the surface of the thermosetting adhesive resin layer (4 ′) described later before curing, when the solar cell back surface protective sheet is formed into a roll after production, blocking tends to occur.
The glass transition temperature here refers to the glass transition temperature measured by differential scanning calorimetry (DSC) for a resin obtained by drying the acrylic polymer emulsion (A) to a solid content of 100%. For example, for the glass transition temperature, an aluminum pan containing a sample obtained by weighing about 10 mg of a sample and an aluminum pan containing no sample are set in a DSC apparatus, and this is set to −50 using liquid nitrogen in a nitrogen stream. A rapid cooling treatment is performed until the temperature is lowered to 100 ° C., and then the DSC curve is plotted. The slope of the DSC curve on the low temperature side (the DSC curve portion in the temperature region where no transition or reaction occurs in the test piece) is extended to the high temperature side, and the slope of the step change portion of the glass transition is maximized. From the intersection with the tangent drawn at such a point, the extrapolated glass transition start temperature (Tig) can be determined, and this can be determined as the glass transition temperature. The glass transition temperature of this invention has described the value measured by said method.

  Next, the blocked polyisocyanate compound (B1) will be described. The polyisocyanate compound (B) constituting the blocked polyisocyanate compound (B1) reacts with the hydroxyl group of the acrylic polymer emulsion (A) to crosslink the copolymers, thereby imparting moisture and heat resistance to the coating film. At the same time, it improves adhesion with a sealing agent such as EVA, which is a sealing agent (IV) on the non-light-receiving surface side that constitutes the solar cell module, and a plastic film (2) that constitutes a solar cell back surface protective sheet described later. Can be made. Therefore, it is important that the polyisocyanate compound (B) has two or more isocyanate groups in one molecule, and examples thereof include aromatic isocyanates, chain aliphatic isocyanates, and alicyclic isocyanates. The polyisocyanate compound (B) may be used alone or in combination of two or more compounds.

  Aromatic polyisocyanates include 1,3-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-triisocyanate. Range isocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4 ', 4 " -Triphenylmethane triisocyanate etc. can be mentioned.

Examples of chain aliphatic polyisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, and dodeca. Examples thereof include methylene diisocyanate and 2,4,4-trimethylhexamethylene diisocyanate.

  Examples of alicyclic polyisocyanates include 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl- Examples include 2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4′-methylene bis (cyclohexyl isocyanate), 1,4-bis (isocyanate methyl) cyclohexane and the like.

  In addition to the polyisocyanate, an adduct of the polyisocyanate and a polyol compound such as trimethylolpropane, a burette or isocyanurate of the polyisocyanate, and further, the polyisocyanate and a known polyether polyol or polyester polyol, Examples thereof include adducts with acrylic polyol, polybutadiene polyol, polyisoprene polyol and the like.

  Furthermore, the blocked isocyanate compound (B1) can be obtained by reacting almost all of the isocyanate groups of the polyisocyanate compound (B) with the blocking agent.

  Examples of the blocking agent include phenols such as phenol, thiophenol, methylthiophenol, xylenol, cresol, resorcinol, nitrophenol, chlorophenol, oximes such as acetone oxime, methyl ethyl ketone oxime, cyclohexanone oxime, methanol, ethanol, n- Alcohols such as propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, t-butyl alcohol, t-pentanol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, benzyl alcohol , 3,5-dimethylpyrazole, 1,2-pyrazole and other pyrazols , Triazoles such as 1,2,4-triazole, halogen-substituted alcohols such as ethylene chlorohydrin and 1,3-dichloro-2-propanol, ε-caprolactam, δ-valerolactam, γ-butyrolactam, β -Active methylene compounds such as lactams such as propyl lactam, methyl acetoacetate, ethyl acetoacetate, acetylacetone, methyl malonate, and ethyl malonate. Other examples include amines, imides, mercaptans, imines, ureas, and diaryls. One blocking agent may be used, or two or more blocking agents may be used in combination.

  It is preferable that the thermosetting adhesive resin layer (4 ') in the solar cell back surface protective sheet of the present invention is uncrosslinked until it is bonded to the sealant layer (IV) to produce a solar cell module. Accordingly, among these blocking agents, those having a dissociation temperature of 80 to 150 ° C. are preferable. When the dissociation temperature is less than 80 ° C., when the thermosetting resin composition is applied and the solvent is volatilized, the curing reaction proceeds and the adhesiveness to the filler may be reduced. When the dissociation temperature exceeds 150 ° C., the curing reaction does not proceed sufficiently in the vacuum thermocompression bonding step when forming the solar cell module, and the adhesion with the filler is lowered.

  Examples of the blocking agent having a dissociation temperature of 80 ° C. to 150 ° C. include methyl ethyl ketone oxime (dissociation temperature: 140 ° C., the same applies hereinafter), 3,5-dimethylpyrazole (120 ° C.), diisopropylamine (120 ° C.), and the like.

  The amount of the polyisocyanate compound (B) in the thermosetting resin composition of the present invention is such that there are 0.1 to 15 isocyanate groups per hydroxyl group in the acrylic polymer. It is necessary to be, and it is more preferable that the range is 0.1 to 10. If it is less than 0.1, the crosslinking density is too low and the heat-and-moisture resistance is not sufficient. If it is more than 15, the excess isocyanate reacts with moisture in the air during the moist heat test, and the coating becomes hard. Moreover, it becomes a cause of the adhesive force fall with the sealing agent with EVA etc. which are sealing agent (IV) on the non-light-receiving surface side which comprises a back surface protection sheet.

  The thermosetting resin composition of the present invention can contain 0.01 to 40 parts by weight, more preferably 0.1 to 40 parts by weight of organic particles or inorganic particles to be described later with respect to 100 parts by weight of the solid content. It can contain -30 weight part. By containing these particles, tackiness on the surface of the thermosetting adhesive resin layer (4 ') before the curing treatment can be reduced. If the content is less than 0.01 parts by weight, tackiness on the surface of the thermosetting adhesive resin layer (4 ') before the curing treatment cannot be sufficiently reduced. On the other hand, when the amount of the various particles increases, the adhesion between the thermosetting adhesive resin layer (4 ') before the curing treatment and the sealant may be hindered, and the adhesive force may be reduced.

  In particular, organic particles having a melting point or softening point of 150 ° C. or higher can be preferably used. When the melting point or softening point of the organic particles is lower than 150 ° C., the particles are softened in the vacuum thermocompression bonding process when the solar cell module is constructed, and there is a possibility that adhesion with the sealant may be hindered.

  Specific examples of the organic particles include polymethyl methacrylate resin, polystyrene resin, nylon (registered trademark) resin, melamine resin, guanamine resin, phenol resin, urea resin, silicon resin, methacrylate resin, acrylate resin and other polymer particles, Alternatively, cellulose powder, nitrocellulose powder, wood powder, waste paper powder, rice husk powder, starch and the like can be mentioned. One type of organic particles may be used, or two or more types may be used in combination.

  The polymer particles can be obtained by a polymerization method such as an emulsion polymerization method, a suspension polymerization method, a dispersion polymerization method, a soap-free polymerization method, a seed polymerization method, or a microsuspension polymerization method. The organic particles may contain impurities to the extent that the characteristics are not impaired. The shape of the particles may be any shape such as powder, granule, granule, flat plate, and fiber.

  Specific examples of inorganic particles include magnesium, calcium, barium, zinc, zirconium, molybdenum, silicon, antimony, titanium, and other metal oxides, hydroxides, sulfates, carbonates, silicates, etc. Inorganic particles to be used. Further specific examples include silica gel, aluminum oxide, calcium hydroxide, calcium carbonate, magnesium oxide, magnesium hydroxide, magnesium carbonate, zinc oxide, lead oxide, diatomaceous earth, zeolite, aluminosilicate, talc, white carbon, mica Glass fiber, glass powder, glass beads, clay, wollastonite, iron oxide, antimony oxide, titanium oxide, lithopone, pumice powder, aluminum sulfate, zirconium silicate, barium carbonate, dolomite, molybdenum disulfide, iron sand, carbon black, etc. Examples thereof include inorganic particles. One type of inorganic particles may be used, or two or more types may be used in combination. Further, the surface of the inorganic particles may be treated with one or two or more inorganic substances or organic substances.

  Moreover, the said inorganic type particle | grain may contain the impurity to such an extent that the characteristic is not impaired. The shape of the particles may be any shape such as powder, granule, granule, flat plate, and fiber.

  Moreover, you may add a crosslinking accelerator to the thermosetting resin composition in this invention in the range which does not prevent the effect by this invention as needed. The crosslinking accelerator plays a role as a catalyst for promoting the urethane bond reaction by the hydroxyl group of the acrylic polymer in the acrylic polymer emulsion (A) and the isocyanate of the polyisocyanate compound (B). Examples of the crosslinking accelerator include tin compounds, metal salts, bases and the like. Specifically, tin octylate, dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, tin chloride, iron octylate, cobalt octylate, and naphthenic acid. Zinc, triethylamine, triethylenediamine and the like can be mentioned. These can be used alone or in combination.

  In addition, the thermosetting resin composition in the present invention includes a filler, a film-forming aid, a thixotropy imparting agent, an anti-aging agent, an antioxidant, an electrification as long as the effects of the present invention are not hindered. Inhibitors, flame retardants, thermal conductivity improvers, plasticizers, anti-sagging agents, antifouling agents, antiseptics, bactericides, antifoaming agents, leveling agents, antiblocking agents, curing agents, thickeners, pigments, dyes Various additives such as a pigment dispersant and a silane coupling agent may be added.

  Moreover, it does not specifically limit as a use of the thermosetting resin composition which concerns on this invention. For example, it can be used as an adhesive for bonding substrates such as plastic film, ethylene-vinyl acetate copolymer, metal, ceramics, glass, wood, paper, and rubber. Furthermore, it can also be used as a coating agent for substrates such as plastic film, metal, ceramics, glass, wood, paper, and rubber.

  Specific examples of the substrate using the emulsion according to the present invention include, for example, plastic films, ethylene-vinyl acetate copolymer films, metals, ceramics, glass, wood, paper, and rubber.

  Examples of the plastic film include polyester resin films such as polyethylene terephthalate, polybutylene terephthalate, and polynaphthalene terephthalate, olefin films such as polyethylene, polypropylene, and polycyclopentadiene, polyvinyl fluoride, polyvinylidene fluoride film, and polytetrafluoroethylene film. Fluorine films such as ethylene-tetrafluoroethylene copolymer films, acrylic films, and triacetyl cellulose films can be used. The plastic film may have a single layer or a multilayer structure of two or more layers. Furthermore, the plastic film may be laminated with a deposited film or the like on which a metal oxide or a non-metallic inorganic oxide is deposited.

  Examples of the metal include hot-rolled steel sheet, cold-rolled steel sheet, hot-dip galvanized steel sheet, electrogalvanized steel sheet, aluminum-plated steel sheet, silver-plated steel sheet, copper-plated steel sheet, alloyed hot-dip galvanized steel sheet, zinc alloy-plated steel sheet, zinc nickel Plated steel sheets such as plated steel sheets, galvanized steel sheets, zinc aluminum plated steel sheets, tin plated steel sheets, zinc alloy plates, stainless steel plates, aluminum plates, copper plates, aluminum alloy plates and the like can be used. There is no distinction between a metal plate and a metal foil in the first metal substrate. There is no limitation in particular as a plating method of the said metal plating base material. As the metal substrate, a material not subjected to so-called chromate treatment may be used. The metal base material may be coated with a rust preventive agent or the like in advance.

  As ceramics, for example, alumina, zirconia, aluminum nitride, silicon carbide, silicon nitride, zinc oxide, forsterite, steatite, cordierite, sialon, barium titanate, lead zirconate titanate, ferrite, mullite, etc. are used. Can do.

  As the glass, for example, soda lime glass, silicate glass, borosilicate glass, aluminosilicate glass, quartz glass and the like can be used.

  As the rubber, for example, natural rubber, synthetic natural rubber, styrene / butadiene rubber, chloroprene rubber, butadiene rubber, acrylonitrile / butadiene rubber, isoprene rubber, silicone rubber, fluorine rubber, urethane rubber and the like can be used.

  As wood and paper, widely known materials can be used. Further, an antiseptic agent or the like may be applied.

  As a specific example of the use of the thermosetting resin composition according to the present invention, for example, a solar cell back surface protective sheet may be mentioned.

FIG. 1 is a schematic cross-sectional view of a solar cell module according to the present invention. The solar cell module 100 includes a solar cell surface protective material (I), a light-receiving surface side sealant (II), a solar battery cell (III), a non-light-receiving surface side sealant (IV), and a solar cell back surface protection. At least the sheet (V) is included. The light receiving surface side of the solar battery cell (III) is protected by the solar cell surface protecting material (I) through the sealant (II) on the light receiving surface side. On the other hand, the non-light-receiving surface side of the solar battery cell (III) is protected by the solar battery back surface protective sheet (V) through the sealant (IV) on the non-light-receiving surface side. The thermosetting resin composition layer which consists of a thermosetting resin composition for solar cell back surface protection sheets is laminated | stacked on the surface layer which touches the solar cell back surface protection sheet (V) of the non-light-receiving surface side.

  In addition, the thermosetting adhesive resin layer (4 ') in the solar cell back surface protective sheet of the present invention undergoes a crosslinking reaction using a thermocompression bonding step when forming the solar cell module 100. In the present invention, the thermosetting resin composition layer before the thermocompression bonding process is distinguished as the thermosetting adhesive resin layer (4 '), and the crosslinked layer after the thermocompression bonding process is differentiated as the curing adhesive layer (4). Similarly, the solar cell back surface protective sheet before the thermocompression bonding step is distinguished as the solar cell back surface protection sheet (V ′), and the solar cell back surface protection sheet after the thermocompression bonding step is distinguished as the solar cell back surface protection sheet (V).

The thermosetting adhesive resin layer (4 ′) in the solar cell back surface protective sheet of the present invention is as uncrosslinked as possible until it is bonded to the sealant layer (IV) to produce a solar cell module. It is preferable to crosslink at the stage of producing. Therefore, the insoluble content of the thermosetting adhesive resin layer (4 ′) with respect to methyl ethyl ketone is preferably 0 to 50% by mass, and more preferably 0 to 25% by mass. If the crosslinking of the thermosetting adhesive resin layer (4 ′) proceeds significantly before the solar cell module manufacturing stage, after the solar cell module is manufactured, the cured adhesive layer (4) and the sealant layer (IV) Adhesion will be reduced.
Here, the insoluble matter with respect to methyl ethyl ketone is expressed by a gel fraction obtained from a mass change before and after stirring in methyl ethyl ketone stirred for 4 hours in refluxing thermosetting adhesive resin layer (4 ′). .

  The thermosetting resin composition of the present invention has good adhesive force with the sealant (IV) by coating the plastic film (2) to form the thermosetting adhesive resin layer (4 ′). A solar cell back surface protective sheet (V ′) can be produced.

  As a method of applying the thermosetting resin composition of the present invention to the plastic film (2), a conventionally known method can be used. Specific examples include comma coating, gravure coating, reverse coating, roll coating, lip coating, and spray coating. By applying the thermosetting resin composition by these methods and volatilizing the solvent by heat drying, the thermosetting adhesive resin layer (4 ') before the curing treatment can be formed. The thickness of the thermosetting adhesive resin layer (4 ′) before the curing treatment is preferably 0.01 to 30 μm, and more preferably 0.01 to 15 μm.

  The thermosetting resin composition of the present invention can also be applied when producing the plastic film (2). Although it does not limit as a manufacturing method of a plastic film, it is especially preferable that it is a biaxial stretching method. By applying at the time of biaxially stretched plastic film production, the adhesion between the plastic film and the thermosetting resin composition is improved, and the production cost can be reduced.

For example, in the simultaneous biaxial stretching method, a method of applying at the time of producing the plastic film is preferably a method in which the film is applied to an amorphous film before stretching, simultaneously biaxially stretched, and then heat-treated. Moreover, in the sequential biaxial stretching method, there are a method in which the film is applied to a film after longitudinal uniaxial stretching and then stretched horizontally and heat-treated, or a method of applying to a film after biaxial stretching and drying. Although there is no restriction | limiting in a method, The method of apply | coating to a uniaxially stretched film, and then extending | stretching laterally, and heat-processing has the characteristics that an application layer can be made thin uniformly, and is preferable.

  Examples of the plastic film (2) include the same plastic films as described above, and polyester resin films are preferable from the viewpoint of rigidity and cost, and among these, polyethylene terephthalate films are preferable. The plastic film (2) may have a single layer or a multilayer structure of two or more layers. Furthermore, the plastic film (2) may be laminated with a deposited film or the like on which a metal oxide or a nonmetal inorganic oxide is deposited.

Examples of the metal oxide or non-metal inorganic oxide to be deposited include oxides such as silicon, aluminum, magnesium, calcium, potassium, tin, sodium, boron, titanium, lead, zirconium, and yttrium. Alkali metal and alkaline earth metal fluorides can also be used, and these can be used alone or in combination.
These metal oxides or non-metal inorganic oxides can be deposited using a conventionally known PVD method such as vacuum deposition, ion plating, sputtering, or the like, or a CVD method such as plasma CVD or microwave CVD.

  The plastic film (2) may be colorless or may contain coloring components such as pigments or dyes. Examples of the method of containing the coloring component include a method of kneading the coloring component in advance at the time of film formation, a method of printing the coloring component on a colorless transparent film substrate, and the like. Further, a colored film and a colorless transparent film may be bonded together.

  The solar cell back surface protective sheet (V ′) is formed on the surface of the plastic film (2) where the thermosetting adhesive resin layer (4 ′) is not formed, with a metal foil (F) or a weather resistant resin layer (G Etc.) may be provided as a single layer or a plurality of layers.

  As the metal foil (F), aluminum foil, iron foil, zinc plywood and the like can be used, and among these, aluminum foil is preferable from the viewpoint of corrosion resistance. The thickness is preferably 10 μm to 100 μm, more preferably 20 μm to 50 μm. Various conventionally known adhesives can be used for laminating the metal foil (F).

  Examples of the weather resistant resin layer (G) include those obtained by laminating polyester resin films such as polyvinylidene fluoride film, polyethylene terephthalate, polybutylene terephthalate, and polynaphthalene terephthalate using various conventionally known adhesives, Asahi Glass Co., Ltd. ) And a coating layer formed by applying a highly weather-resistant paint such as Lumiflon.

Next, the solar cell module will be described.
The solar cell module 100 seals the solar cell surface protection material (I) positioned on the light receiving surface side of the solar cell with respect to the solar cell (III) before the curing process positioned on the light receiving surface side of the solar cell. The solar cell back surface protection sheet (V ′) before curing treatment is laminated via the sealing agent (IV) before curing treatment positioned on the non-light-receiving surface side of the solar battery cell. It can be obtained by hot pressing under reduced pressure.

  Although it does not specifically limit as solar cell surface protective material (I), A glass plate, a plastic plate of polycarbonate or polyacrylate etc. can be mentioned as a suitable example. In view of transparency, weather resistance, toughness and the like, a glass plate is preferable. Furthermore, white glass with high transparency is preferable among the glass plates.

The sealing agent (II) located on the light receiving surface side of the solar cell and the sealing agent (IV) located on the non-light receiving surface side are not particularly limited, and known materials can be suitably applied. Suitable materials include EVA (ethylene-vinyl acetate copolymer), polyvinyl butyral, polyurethane, polyolefin and the like. Of these, EVA is mainly used from the viewpoint of cost. As the sealing agents (II) and (IV), a sheet (including a film) is simple, but a paste or the like may be used.
Although it does not specifically limit in the sealing agent (II) located in the light-receiving surface side, and the sealing agent (IV) located in the non-light-receiving surface side, the organic peroxide may be contained. By containing the organic peroxide, when the solar battery cell (III) is sandwiched between the sealing agents (II) and (IV) and heated, the sealing agent (II) is crosslinked or sealed by a radical reaction. Crosslinking the agent (II) and the sealant (IV) or crosslinking the sealant (IV) can be performed with high efficiency.

  Examples of the organic peroxide contained in the sealant include tert-butyl peroxyisopropyl carbonate, tert-butyl peroxy-2-ethylhexyl isopropyl carbonate, tert-butyl peroxyacetate, tert-butylcumyl peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 1,1-di (tert-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (tert- Butylperoxy) cyclohexane, 1,1-di (tert-hexylperoxy) C) Cyclohexane, 1,1-di (tert-amylperoxy) cyclohexane, 2,2-di (tert-butylperoxy) butane, methyl ethyl ketone peroxide, 2,5-dimethylhexyl-2,5-diperoxy Benzoate, tert-butyl hydroperoxide, dibenzoyl peroxide, p-chlorobenzoyl peroxide, tert-butylperoxyisobutyrate, n-butyl-4,4-di (tert-butylperoxy) valerate, ethyl- 3,3-di (tert-butylperoxy) butyrate, hydroxyheptyl peroxide, dichlorohexanone peroxide, 1,1-di (tert-butylperoxy) 3,3,5-trimethylcyclohexane, n-butyl-4 , 4-di (tert Butyl peroxy) valerate, 2,2-di (tert- butylperoxy) butane, and the like. These organic peroxides can be contained in the encapsulant by, for example, adding the encapsulant resin when the sheet is processed, and melt-kneading.

  As the solar cell (III), an electrode is provided on a photoelectric conversion layer such as crystalline silicon, amorphous silicon, and a compound semiconductor represented by copper indium selenide, and further, these are laminated on a substrate such as glass. Etc. can be illustrated.

<Synthesis of Acrylic Polymer Emulsion A1>
In a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer and a dropping layer, 90 parts of water was added and the temperature in the reaction vessel was raised to 85 ° C., and then 0.2 part of potassium persulfate was added.
Next, 50 parts of water, 2 parts of methyl methacrylate (hereinafter referred to as MMA), 93 parts of n-butyl methacrylate (hereinafter referred to as BMA), 5 parts of 1,4-cyclohexanedimethanol monomethacrylate (hereinafter referred to as CHDMMA), poly 1.5 parts of a 20% aqueous solution of ammonium oxyalkylene alkyl ether sulfate (product name: Eleminol CLS-20 [manufactured by Sanyo Chemical Industries, Ltd.]) and polyoxyethylene alkyl ether (product name: Emulgen E1118S-70 [Kao] A mixed solution obtained by mixing 2 parts of a 25% aqueous solution of [made by Co., Ltd.] was dropped into the reaction vessel over 2 hours from the dropping layer.
During the dropping, the temperature in the reaction vessel was kept at 80 ° C. After completion of dropping, the temperature in the reaction vessel was raised to 85 ° C. and held for 30 minutes.
Next, the temperature in the reaction vessel is cooled to 62 ° C., 1 part of a 5% aqueous solution of tert-butyl hydroperoxide and 2 parts of a 1% aqueous solution of sodium isoascorbate are added successively, and the temperature in the reaction vessel is changed to 62. Hold at 30 ° C. for 30 minutes. Finally, it was cooled to room temperature, adjusted to pH 8 by adding 25% aqueous ammonia, and then filtered through a nylon mesh. The obtained emulsion had a solid content of 40% and an average particle size of 150 nm.
The glass transition temperature and hydroxyl value were measured as described below.

<Synthesis of acrylic polymer emulsions A2 to A37 and B1 to B7>
Acrylic polymer emulsions A2 to A37 and B1 to B7 were obtained in the same manner as acrylic polymer emulsion A1 except that the mixture of acrylic monomers was changed to the composition shown in Table 2.

<Measurement of glass transition temperature (Tg)>
The glass transition temperature was measured by a differential scanning calorimetry (DSC) method.
The glass transition temperature here refers to the glass transition temperature measured by differential scanning calorimetry (DSC) for a sample obtained by drying the acrylic polymer emulsion (A) to a solid content of 100%. For example, for the glass transition temperature, an aluminum pan containing a sample obtained by weighing about 10 mg of a sample and an aluminum pan containing no sample are set in a DSC apparatus, and this is set to −50 using liquid nitrogen in a nitrogen stream. A rapid cooling treatment is performed until the temperature is increased to 100 ° C. at 20 ° C./min, and a DSC curve is plotted. The slope of the DSC curve on the low temperature side (the DSC curve portion in the temperature region where no transition or reaction occurs in the test piece) is extended to the high temperature side, and the slope of the step change portion of the glass transition is maximized. From the intersection with the tangent drawn at such a point, the extrapolated glass transition start temperature (Tig) can be determined, and this can be determined as the glass transition temperature. The glass transition temperature of this invention has described the value measured by said method. In addition, the sample for Tg measurement used what heated said acrylic resin solution at 150 degreeC for about 15 minutes, and was made to dry.

<Measurement of hydroxyl value (OHV)>
(1) Hydroxyl value of solid content of acrylic polymer emulsion As in the case of the above Tg measurement, about 1 g of a sample obtained by drying an acrylic polymer emulsion to a solid content of 100% was accurately weighed in a stoppered flask. Add 100 ml of pyridine and dissolve at 100 ° C. Further, exactly 5 ml of an acetylating agent (a solution in which 25 g of acetic anhydride was dissolved in pyridine to make a volume of 100 ml) was added and stirred at 100 ° C. for about 1 hour. To this, phenolphthalein reagent is added as an indicator and lasts for 30 seconds. Thereafter, the solution is titrated with a 0.5N alcoholic potassium hydroxide solution until the solution becomes light red.
The hydroxyl value was determined by the following formula. The hydroxyl value was a numerical value in the dry state of the resin (unit: mgKOH / g).
Hydroxyl value (mgKOH / g) = [{(ba) × F × 28.05} / S] / (Nonvolatile content concentration / 100) + D
Where S: Amount of sample collected (g)
a: Consumption of 0.5N alcoholic potassium hydroxide solution (ml)
b: Consumption of the 0.5N alcoholic potassium hydroxide solution in the blank experiment (ml)
F: Potency of 0.5N alcoholic potassium hydroxide solution D: Acid value (mgKOH / g)

(2) Hydroxyl value of water-insoluble component in acrylic polymer emulsion After centrifuging the acrylic polymer emulsion in a centrifuge (30000 rpm, 1 hour), the supernatant is removed and the same amount as the removed supernatant Of water was added again to perform centrifugation (30000 rpm, 1 hour), the supernatant solution was removed, and the precipitated components were dried to obtain water-insoluble components. The hydroxyl value of the obtained water-insoluble component was determined in the same manner as (1) above.

As shown in Table 2, since the acrylic emulsions A1 to A10 used an acrylic monomer having a hydroxyl group whose solubility in water is 75 μg / mL or less, the hydroxyl value per 100 parts by mass of the water-insoluble component is an emulsion. It represents 95% or more of the hydroxyl value per 100 parts by mass of the solid content. That is, most of the acrylic monomers having a hydroxyl group used are incorporated in the water-insoluble component. In particular, when the solubility of the acrylic monomer having a hydroxyl group in water is 24 μg / mL or less, 97% or more of the acrylic monomer having a hydroxyl group used is incorporated in the water-insoluble component.
On the other hand, the acrylic emulsions B1 and B2 use an acrylic monomer having a hydroxyl group having a solubility in water of more than 75 μg / mL, so that only about 70% is incorporated in the water-insoluble component, and nearly 30% is water-soluble. It exists in the water phase as a sex component.

[Examples 1 to 10], [Comparative Examples 1 and 2]
<Adjustment of thermosetting resin composition PA1-PA10, PB1-PB2>
Emulsions of acrylic polymers shown in Table 2 A1 to A10, B1 to B2 (emulsions using hydroxyl acrylic monomers having different solubility in water at 25 ° C.) and blocked polyisocyanate compound (B1) (product name: Imprafix 2794XP (manufactured by Bayer MaterialScience AG)) was mixed at a ratio such that the hydroxyl group and isocyanate were about 1: 1 to obtain thermosetting resin compositions PA1 to PA10 and PB1 to PB2.

<Gel fraction>
Using the thermosetting resin compositions PA1 to PA10 and PB1 to PB2 prepared in Examples 1 to 10 and Comparative Examples 1 to 2, each was applied to a PET film, heated at 100 ° C. for 1 minute, and dried to be thermosetting. An adhesive resin layer was obtained. The thickness of the thermosetting adhesive resin layer was 10 μm. Thereafter, each thermosetting adhesive resin layer was peeled off from the PET film, and the peeled thermosetting adhesive resin layer was sandwiched between metal meshes and stirred in refluxed methyl ethyl ketone for 4 hours. Thereafter, the metal mesh was taken out and dried, and the gel fraction was determined from the mass change before and after reflux. The gel fraction was calculated from the following formula.
Gel fraction (%) = 100 × (BM) / A
A: Thermosetting resin layer mass before reflux B: Metal mesh after reflux + mass of cured product M: Mass of metal mesh

<Creation of Back Protective Sheets BSA1 to BSA10 and BSB1 to BSB2 for Solar Cells>
Each thermosetting resin composition PA1-PA10, PB1-PB2 is applied to a polyester film (product name: Lumirror X10S, film thickness 125 μm [manufactured by Toray Industries, Inc.]) with a bar coater, and heated at 100 ° C. for 1 minute. The solvent was dried to obtain solar cell backsheets BSA1 to BSA10 and BSB1 to BSB2. The amount of each dried thermosetting resin composition layer was 3 g / m ² and the adhesive strength was evaluated as follows. The results are shown in Table 3.

<Adhesive strength evaluation>
White thermoset glass, vinyl acetate-ethylene copolymer film (manufactured by Sunvic Co., Ltd., fast cure type, hereinafter referred to as EVA film), back protection sheet BSA1 for each solar cell, etc., each thermosetting resin composition layer as an EVA film It was piled up in order to touch. Thereafter, this laminate is put into a vacuum laminator, evacuated to about 1 Torr, heated at 150 ° C. for 30 minutes at a press pressure of 0.1 MPa, and further heated at 150 ° C. for 30 minutes, and then each thermosetting resin composition. The layer was cured to obtain a 10 cm × 10 cm square adhesive strength evaluation sample SA1 and the like.

<Adhesion measurement>
About each sample for adhesive strength evaluation, after leaving still for 1000 hours, 2000 hours, and 3000 hours under the environmental conditions of an initial temperature of 85 ° C. and a relative humidity of 85% RH, the SA1 solar cell backsheet BSA1 surface is 10 mm wide with a cutter. The adhesive force between the easy-adhesive layer formed on the solar battery backsheet BSA1 and the EVA film as the sealant was measured. For the measurement, a tensile tester was used and a 180 degree peel test was performed at a load speed of 100 mm / min. The obtained measurement values were evaluated as follows.
A: 40 N / 10 mm or more B: 30 N / 10 mm or more to less than 40 N / 10 mm Δ: 10 N / 10 mm or more to less than 30 N / 10 mm x: less than 10 N / 10 mm

[Comparative Example 3]
A polyester film (product name: Lumirror X10S, film thickness 125 μm [manufactured by Toray Industries, Inc.]) is used as a solar cell back surface protection sheet BSB3, white plate glass, vinyl acetate-ethylene copolymer film (manufactured by Sunvic Co., Ltd., Fast Cure) Type, hereinafter referred to as EVA film), and back surface protection sheet BSB3 for solar cells were stacked in order so that each thermosetting resin composition layer was in contact with the EVA film. Thereafter, this laminate is put into a vacuum laminator, evacuated to about 1 Torr, heated at 150 ° C. for 30 minutes at a press pressure of 0.1 MPa, and further heated at 150 ° C. for 30 minutes, and then each thermosetting resin composition. The layer was cured to obtain a 10 cm × 10 cm square adhesive strength evaluation sample SB3.

<Adhesion measurement>
About the sample for adhesive strength evaluation, after leaving still for 1000 hours, 2000 hours, and 3000 hours under the environmental conditions of a temperature of 85 ° C. and a relative humidity of 85% RH, the SA1 solar cell backsheet BSA1 surface is made 10 mm wide with a cutter. The adhesive force between the easy-adhesive layer formed on the solar battery backsheet BSA1 and the EVA film as the sealant was measured. For the measurement, a tensile tester was used and a 180 degree peel test was performed at a load speed of 100 mm / min. The obtained measurement values were evaluated as follows.
A: 40 N / 10 mm or more B: 30 N / 10 mm or more to less than 40 N / 10 mm Δ: 10 N / 10 mm or more to less than 30 N / 10 mm x: less than 10 N / 10 mm

<Adhesiveness after wet heat resistance test>
Adhesive strength evaluation sample SA1 was allowed to stand for 1000 hours, 2000 hours, and 3000 hours under environmental conditions of a temperature of 85 ° C. and a relative humidity of 85% RH, and then evaluated for adhesiveness after a wet heat resistance test in the same manner as the adhesiveness measurement. Went.

As shown in Table 3, since Examples 1 to 10 use an acrylic monomer (a1) having a hydroxyl group having a solubility in 25 ° C. water of 75 μg / mL or less, the adhesiveness after the wet heat resistance test is excellent. Moreover, since the gel fraction of the thermosetting adhesive resin layer (4 ′) was 0 to 50%, the adhesion after thermosetting is excellent.
On the other hand, Comparative Examples 1 to 3 are inferior in adhesion after the wet heat resistance test, although the initial adhesion is excellent.

[Examples 11 to 21], [Comparative Examples 4 to 6]
<Creation of Back Surface Protection Sheets BSA11 to BSA21 and BSB4 to BSB6 for Solar Cells>
Thermosetting resin compositions PA11 to PA21 and PB4 to PB6 comprising acrylic polymers A11 to 21 and B3 to B5 having different glass transition temperatures instead of the acrylic polymer A1 having a glass transition temperature of about 21 ° C. BSA11 to BSA21 and BSB4 to BSB6 were obtained and evaluated in the same manner as in Example 1 except that they were used. The results are shown in Table 4. In addition, blocking property evaluation is as follows.

<Evaluation of blocking properties>
A polyester film (product name: Lumirror X10S, film thickness 125 μm [manufactured by Toray Industries, Inc.]) was layered on the thermosetting resin composition layer of the back protective sheet for solar cells having a size of 40 mm × 40 mm, and a load of 64 kg was applied. . The polyester film was peeled off after being left for 1 week at 60 ° C. while maintaining a load of 64 kg, and the area ratio of the thermosetting resin composition layer transferred to the polyester film was evaluated as follows.
○: Blocking less than 5% Δ: Blocking 5% or more and less than 50% ×: Blocking 50% or more and 100% or less

  As shown in Table 4, in Examples 1 and 11 to 21, since the Tg of the acrylic polymer emulsion (A) is −40 to 100 ° C., the initial and excellent adhesiveness after the heat and humidity resistance test are excellent. Furthermore, since Tg of Examples 12-20 is -30-90 degreeC of acrylic polymer emulsion (A), the adhesiveness after an initial stage and a moist heat test is further excellent. Moreover, it is excellent in blocking property. In particular, since Examples 13 to 19 have a Tg of -20 to 70 ° C, the adhesiveness at the initial stage and after the wet heat resistance test is more excellent.

[Examples 22 to 33], [Comparative Example 7]
<Creation of Back Protective Sheets for Solar Cells BSA22 to BSA33, BSB7>
Acrylic polymer emulsions A22 to 33, B7 having different hydroxyl values are used instead of the acrylic polymer emulsion A1 having a hydroxyl value of about 14.6 (mgKOH / g) per 100 parts of the water-insoluble component in the emulsion. BSA22 to BSA33 and BSB7 were obtained and evaluated in the same manner as in Example 1 except that the thermosetting resin compositions PA22 to PA33 and PB7 were used. The results are shown in Table 5.
B7 did not use the blocked polyisocyanate compound (B1).

  As shown in Table 5, in Examples 1 and 23 to 32, since the hydroxyl value of the acrylic polymer emulsion (A) is 1 to 150 mgKOH / g, the adhesiveness at the initial stage and after the wet heat resistance test is excellent. Furthermore, since Examples 1 and 23 to 31 have a hydroxyl value of 1 to 120 mgKOH / g in the acrylic polymer emulsion (A), the adhesion after the initial and wet heat resistance tests is further improved. Since the hydroxyl value of the acrylic polymer emulsion (A) is 1 to 100 mgKOH / g, the adhesiveness after the initial and wet heat resistance tests is more excellent.

[Examples 34 to 43], [Comparative Example 8]
<Creation of Back Protective Sheets for Solar Cells BSA34 to BSA43, BSB8>
Acrylic polymer emulsion A1 and a blocked polyisocyanate compound (B) (product name: Imprafix 2794XP [manufactured by Bayer MaterialScience AG]) were used except that the ratio of the hydroxyl group to the isocyanate was the ratio shown in Table 6. In the same manner as in Example 1, thermosetting resin compositions PA34 to PA43 and PB8 were obtained. The results are shown in Table 6.

  As shown in Table 6, since Examples 1 and 34 to 42 have NCO / OH = 0.1 to 15, the adhesion after the initial stage and after the moist heat resistance test is excellent. Furthermore, since Example 1 and 34-40 are NCO / OH = 0.1-10, the adhesiveness after an initial stage and a wet heat test is further excellent.

[Examples 44 to 47]
<Creating a back for a solar cell protective sheet BSA44~BSA4 7>
As an acrylic monomer having a hydroxyl value, CHDMMA, which is an acrylic monomer having a solubility in water of 75 μg / ml or less, and HEMA having a solubility in water of 200 μg / ml are used in place of the acrylic polymer emulsion A1. and formed by using an acrylic polymer A34～ 37 comprising, except that had use a thermosetting resin composition PA44～PA 47 may give BSA44～BSA4 7 in the same manner as in example 1, was evaluated in the same manner. The results are shown in Table 7.

As shown in Table 7, even when an acrylic monomer having a hydroxyl group having a solubility in water of 75 μg / mL or less and an acrylic monomer having a hydrophilic hydroxyl group are used in combination, the solubility in water is 75 μg / mL. If the hydroxyl value derived from the acrylic monomer having the following hydroxyl group exceeds 5% of the hydroxyl value of the emulsion, the heat and moisture resistance is excellent. On the other hand, when the hydroxyl value derived from an acrylic monomer having a hydroxyl group having a solubility in water of 75 μg / mL or less is 5% or less of the hydroxyl value of the emulsion, that is, the hydroxyl value derived from an acrylic monomer having a hydrophilic hydroxyl value is In the case of 95% or more, the heat and humidity resistance is relatively deteriorated.

[Examples 48 to 57], [Comparative Examples 10 to 11]
Thermosetting resin compositions PA1 to PA10 and PB1 to PB2 prepared in Examples 1 to 10 and Comparative Examples 1 to 2 on a polyester film (product name: Lumirror X10S, film thickness 125 μm [manufactured by Toray Industries, Inc.]) After coating with a coater and heating at 100 ° C. for 1 minute to dry the solvent, each of the copper plate, aluminum plate and glass plate was laminated so that the thermosetting resin composition was in contact. Thereafter, this laminate is put into a vacuum laminator, evacuated to about 1 Torr, heated at 150 ° C. for 30 minutes at a press pressure of 0.1 MPa, and further heated at 150 ° C. for 30 minutes, and then each thermosetting resin composition. The layer was cured to obtain an adhesive strength evaluation sample SA48 and the like.

<Adhesion measurement>
About the sample for adhesive strength evaluation, after leaving still for 3000 hours under the environmental conditions of an initial temperature of 85 ° C. and a relative humidity of 85% RH, the polyester film surface, which is a coating substrate such as SA48, is cut to a width of 10 mm with a cutter, and polyester The adhesive force between the easy-adhesive layer formed on the film surface and each of the laminated substrates, ie, a copper plate, an aluminum plate, and a glass plate was measured. For the measurement, a tensile tester was used and a 180 degree peel test was performed at a load speed of 100 mm / min. With respect to the obtained measured value, the adhesive strength reduction rate after the environmental condition with respect to the initial stage was calculated and evaluated as follows.
Adhesion rate reduction rate (%) = 100 × (1− (adhesive strength after environmental conditions) / (initial adhesive strength))
A: Adhesive strength reduction rate 0% or more to less than 10% B: Adhesive strength reduction rate 10% or more to less than 30% Δ: Adhesion strength reduction rate 30% or more to less than 60% X: Adhesion strength reduction rate 60% or more to 100 %Less than

  As shown in Table 8, since the solubility of the acrylic monomer having a hydroxyl group in water in Examples 48 to 57 is 75 μg / mL or less, the decrease in adhesion is small even after the wet heat resistance test. Further, Examples 48 to 53 and Examples 55 to 57 are further excellent because the solubility of the acrylic monomer having a hydroxyl group in water is 32 μg / mL or less, and in particular, Examples 48 to 52 and Examples 55 to 55 are used. 57 is particularly excellent because the solubility of an acrylic monomer having a hydroxyl group in water is 32 μg / mL or less. On the other hand, in Comparative Examples 10 and 11, since the solubility of the acrylic monomer having a hydroxyl group in water is greater than 75 μg / mL, the adhesiveness is greatly reduced in any combination with any substrate.

[Examples 58 to 67], [Comparative Examples 12 to 13]
The thermosetting resin compositions PA1 to PA10 and PB1 to PB2 prepared in Examples 1 to 10 and Comparative Examples 1 to 2 were used to coat steel plates, aluminum plates, polyethylene terephthalate (hereinafter referred to as PET) films, and glass plates, respectively. And heated at 150 ° C. for 30 minutes to cure the thermosetting resin composition layer. The thickness of the cured layer was 10 μm.
Adhesion, whitening resistance, gel fraction, and solvent resistance were evaluated by the following methods. The results are shown in Table 9.

<Adhesion evaluation>
Let stand for 3000 hours under environmental conditions of temperature 85 ° C and relative humidity 85% RH, create a test piece with a cross-cut according to the cross-cut test method described in the former JIS K5400, and use cellophane tape. After pasting on the grid of the test piece, it was quickly pulled and peeled in the direction of 90 °, and the number of grids that were not peeled in the grid 100 was counted and evaluated as follows.
A: Peeling area 0%
◯: Greater than 0%, less than 5% △: Greater than 5%, less than 15% x: Greater than 15%, less than 35% xx: Greater than 35%, less than 100%

<Whitening resistance evaluation>
About the sample after leaving still for 3000 hours on the environmental conditions of temperature 85 degreeC and relative humidity 85% RH, the whitening area of the hardened layer was confirmed visually and evaluated as follows.
A: Whitening area 0% or more, less than 10% B: Whitening area 10% or more, less than 40% Δ: Whitening area 40% or more, less than 70% ×: Whitening area 70% or more, 100% or less

<Evaluation of gel fraction and solvent resistance>
Each cured layer was peeled from the PET film, the peeled cured layer was sandwiched between metal meshes, and stirred in refluxed methyl ethyl ketone for 4 hours. Thereafter, the metal mesh was taken out and dried, and the gel fraction was determined from the mass change before and after reflux. The gel fraction was calculated from the following formula.
Gel fraction (%) = 100 × (BM) / A
A: Amount of cured substance before reflux B: Metal mesh after reflux + mass of cured product M: Mass of metal mesh The solvent resistance was evaluated as follows with respect to the gel fraction.
◎: 80% to 100% ○: 50% to less than 80% △: 20% to less than 50% ×: 0% to less than 20%

As shown in Table 9, Examples 58 to 67 are excellent in adhesion and whitening resistance even after a moist heat test because the solubility of an acrylic monomer having a hydroxyl group in water is 75 μg / mL or less. 58-63 and Examples 65-67 are further excellent because the solubility of the acrylic monomer having a hydroxyl group in water is 32 μg / mL or less. On the other hand, Comparative Examples 12 and 13 have good adhesion to PET but poor whitening resistance.
Moreover, since Examples 58-67 used the monomer whose solubility to water is 75 microgram / mL or less as an acrylic monomer which has a hydroxyl group, while the gel fraction of a hardened layer exceeds 80%, solvent resistance is made. Excellent. In particular, when the solubility of the acrylic monomer having a hydroxyl group in water is 24 μg / mL or less, the gel fraction exceeds 87% and the solvent resistance is particularly excellent. On the other hand, the acrylic emulsions B1, 2 have a gel fraction of 20% or less and poor solvent resistance because the solubility of the acrylic monomer having a hydroxyl group used in water is greater than 75 μg / mL.

  The thermosetting resin composition of the present invention is suitably used for forming the thermosetting adhesive resin layer (4 ′) as the outermost surface layer constituting the solar cell back surface protective sheet, and is in close contact with various substrates. Since a cured coating film with excellent properties can be formed, it can be applied to various paints and various adhesives.

DESCRIPTION OF SYMBOLS 100 ... Solar cell module (I) ... Solar cell surface protection member (II) ... Light-receiving surface side sealing agent layer (III) ... Solar cell (IV) ... Non-light-receiving surface side Sealant layer (V) ... solar cell back surface protective sheet (2) ... plastic film (1) ... weather resistant resin layer (3) ... metal foil (4 ') ... thermosetting Adhesive resin layer (4 ')

Claims (5)

A solar cell back surface protective sheet having a thermosetting adhesive resin layer (4 ′) as an outermost surface layer on one surface of a plastic film (2),
The thermosetting adhesive resin layer (4 ′) is
A glass transition temperature obtained by polymerizing an acrylic monomer (a) having a hydroxyl group and having a hydrophobic acrylic monomer (a1) having a solubility in water at 25 ° C. of 75 μg / mL or less as an essential component in an aqueous medium is − It is formed from a thermosetting resin composition containing an acrylic polymer emulsion (A) at 40 ° C. to 100 ° C. and a blocked polyisocyanate compound (B1),
The insoluble content with respect to methyl ethyl ketone of the thermosetting adhesive resin layer (4 ′) is 0 to 50% by weight,
Solar cell back surface protection sheet.   The hydroxyl value of the solid content of the acrylic polymer emulsion (A) is 1 to 200 mgKOH / g, and the hydroxyl value of the water-insoluble component contained in the acrylic polymer emulsion (A) is 1 to 150 mgKOH / g. The solar cell back surface protection sheet of 1. Hydrophobic acrylic monomer (a1) having a hydroxyl group and solubility in water at 25 ° C. of 75 μg / mL or less is polypropylene glycol monoacrylate, polypropylene glycol monomethacrylate, 4-hydroxybutyl methacrylate, 1,4-cyclohexanedimethanol Consists of monoacrylate, 1,4-cyclohexanedimethanol monomethacrylate, 2-hydroxybutyl acrylate, 2-hydroxybutyl methacrylate, polypropylene glycol monomethacrylate, 5-hydroxypentyl methacrylate, and unsaturated fatty acid hydroxyalkyl ester modified ε-caprolactone The solar cell back surface protection sheet of Claim 1 or 2 which is at least 1 type chosen from a group.   The molar ratio between the hydroxyl group in the acrylic polymer and the isocyanate group in the blocked polyisocyanate compound (B1) is NCO / OH = 0.1 to 15, according to any one of claims 1 to 3. Solar cell back surface protection sheet. Solar cell surface protection member (I) located on the light-receiving surface side of the solar cell, sealant layer (II) located on the light-receiving surface side of the solar cell, solar cell (III), on the non-light-receiving surface side of the solar cell It comprises the solar cell back surface protection sheet according to any one of claims 1 to 4, which is in contact with the sealant layer (IV) positioned and the non-light-receiving surface side sealant layer (IV). A solar cell module,
The solar cell module, wherein the cured adhesive layer (4) formed from the curable adhesive resin layer (4 ') is in contact with the non-light-receiving surface side sealing agent layer (IV).